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## Dilations

Current time:0:00Total duration:2:46

# Performing dilations

CCSS Math: HSG.SRT.A.1, HSG.SRT.A.1b

## Video transcript

Perform a dilation on
the coordinate plane. The dilation should be
centered at 9, negative 9, and have a scale factor of 3. So we get our dilation tool out. We'll center it-- actually, so
it's already actually centered at 9, negative 9. We could put this
wherever we want, but let's center it
at 9, negative 9. And we want to
scale this up by 3. So one way to think about it
is, pick any of these points right over here, and they're
going to have to get 3 times further away from our
center of dilation. So for example, this
point C-- actually let's think about these
points where they actually want us to fill something in. So point A right over here, it
is at the point 4, negative 3. So in the x direction,
it is 5 less than 9. We want it to be 3
times further than 9. So we want it to
be 15 less than 9. So we want the x-coordinate of
A, 9 minus 15 is negative 6. We want it to go to negative 6. And likewise, we want its
y-coordinate to be 3 times further. So right now, let's
see, it is at negative 3 relative to negative 9, so it
is 6 more on the y direction. We want it to be 18 more. 18 more than negative
9 would be positive 9. So point A should map
to negative 6 comma 9. And that should give
us enough information to just make sure that we are
dilating up by a factor of 3. So let's see. Let's dilate up
by a factor of 3. So we want to get the image of
point A to the point negative 6 comma 9. So we are there. There we go. We have dilated it up. And then we could
even look where the point that corresponds
to E has mapped to. And you can look at each
direction, it's 3 times further. E is now at negative
6 comma negative 3. The images of point A
and E are 3 times as far as the original points. 3 times far apart, I should
say, as the original points. And they're 3 times further
from our center of dilation right over here. You see, for example, point
E has the x-coordinate of 4, which is 5 less. Now it is at
negative 6, which is 15 less than our
center of dilation. And the same thing true,
its y-coordinate is 2 more. And now after we mapped
it, its y-coordinate is 6 more than our
center of dilation. Got it right.